1. Field of the Invention
The present invention relates to the field of angioplasty. In particular, the present invention relates to a dilatation balloon catheter of the "over-the-wire" type.
2. Description of the Prior Art
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular disease. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Typically, a hollow guide catheter is used in guiding the dilatation catheter through the vascular system to a position near the stenosis (e.g. to the aortic arch). Using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to reestablish acceptable blood flow through the artery.
There has been a continuing effort to reduce the profile and shaft size of the dilatation catheter so that the catheter not only can reach but also can cross a very tight stenosis. A successful dilatation catheter must also be sufficiently flexible to pass through tight curvatures, especially in the coronary arteries. A further requirement of a successful dilatation catheter is its "pushability". This involves the transmission of longitudinal force along the catheter from its proximal end to its distal end so that a physician can push the catheter through the vascular system and the stenosis.
Two commonly used types of dilatation catheters are referred to as "over-the-wire" catheters and "non-over-the-wire" catheters. An over-the-wire catheter is one in which a separate guide wire lumen (sometimes called a "thru lumen") is provided so that a guide wire can be used to establish the path through the stenosis. The dilatation catheter can then be advanced over the guide wire until the balloon is positioned within the stenosis. One problem with the over-the-wire catheter is the requirement of a larger profile and a generally larger outer diameter along its entire length in order to allow for a separate guide wire lumen.
A non-over-the-wire catheter acts as its own guide wire, and thus there is no need for a separate guide wire lumen. One advantage of a non-over-the-wire catheter is its potential for a reduced outer diameter along its main shaft since a guide wire lumen is not required. However, one disadvantage is the inability to maintain the position of a guide wire within the vascular system when removing the catheter and exchanging it for one of a smaller (or larger) balloon diameter. Thus, to accomplish an exchange with the non-over-the-wire catheter, the path to the stenosis must be reestablished when replacing the catheter with one having a different balloon diameter.
It is desirable in some cases to feed two dilatation catheters through the same guide catheter simultaneously. This procedure is used, for example, to inflate both sides of a Y branch in the coronary arteries. In the past, only non-over-the-wire catheters have been small enough to be used for this type of procedure. In general, the need for providing two lumens in an over-the-wire catheter has resulted in a larger outer diameter along its entire length so that it is not possible to feed two over-the-wire catheters through a typical 8 French (8F) guide catheter at the same time.